The present invention relates to a microcomputer and, more particularly, to a single chip microcomputer including a serial data communication unit.
As well known in the art, serial data transfer is widely employed as one of data communication methods between a microcomputer and a peripheral device such as a memory. The microcomputer thus includes a serial data communication unit as an I/O (Input/Output) unit.
While the CPU (Central Processing Unit) in the microcomputer manages or controls the serial data communication unit, the actual data transfer is carried out between the serial data communication unit and the peripheral device. Therefore, the CPU treats the serial data communication unit as an asynchronous I/O unit. In other words, CPU responds to a request from the serial data communication unit and then sets therein data to be transferred to the peripheral device or reads out therefrom data transferred from the peripheral device. Since the CPU continues to execute instructions for a program, in order to respond to the request it must suspend the program execution and then perform the above operation as an interrupt routine. The program execution efficiency and/or speed is thereby deteriorated.